Acid diffusion during the post-exposure bake of chemically amplified resists (CARs) is a major contributing factor to
line width roughness (LWR) and resolution limits at the 32 nm node and beyond. To overcome these limitations,
non-CAR materials are becoming more attractive because acid diffusion is eliminated. We have therefore focused our
effort on the synthesis of copolymers that have both a diacyldiazo side chain unit as well as a hexafluoroalcohol unit.
This copolymer shows better contrast than that of copolymers containing lactone units due to their inhibition behavior.
Furthermore, polymer blends containing hexafluoroalcohol groups show good 100 nm line and space patterning property
for 193 nm lithography. This paper describes the design, synthesis, and characterization of these non-CARs, and thier
improvement to photolithography.
ArF immersion lithography using water as a fluid medium enables production of 45 nm features. Extending immersion lithography to 32 nm or below requires increases in the refractive indices of the lens material, the immersion fluid, and the resist material. However, a material with a high refractive index generally also has high absorbance. In attempt to design a resist with high refractive index and low absorbance, we studied several types of sulfur-containing polymers and determined which sulfur groups increase the refractive index without increasing the absorbance at 193 nm. We describe new thioester and sulfone structures that enable high index with low absorbance. This chemistry has been exploited to produce polymers with a refractive index of 1.8 at 193 nm and an absorbance less than 1.4 &mgr;m-1. The compatibility of the sulfur functionality with chemically amplified imaging chemistry was demonstrated by printing at 193 nm.
In immersion lithography a fluid with a high refractive index is used to enable increases in the numerical aperture (NA) of the imaging system and therefore decrease the minimum feature size that can be patterned. Water has been used in first generation immersion lithography at 193 nm for the 45 nm node. To generate still smaller features, fluids with a higher index than water are needed. Both saturated hydrocarbons and a new class of salts with incorporated alkane groups have been studied. Both of these types of fluids possess the "adjustable" absorbance edge behavior needed to provide a fluid with a high index and low absorbance at 193 nm. Since alkanes have physical properties that are difficult to integrate into current fluid handling systems, the aqueous solutions are particularly attractive as more semiconductor-friendly fluids. A full characterization of the optical properties of these fluids will be reported, as well as physical property results and confirmation of the feasibility of 32 nm l/s imaging with 1.5 NA using the salt solutions.